If $x \oplus y = x^{2}+4y^{2}$ and $x \bigtriangleup y = x-5y$, find $-4 \oplus (-1 \bigtriangleup 0)$.
Solution: First, find $-1 \bigtriangleup 0$ $ -1 \bigtriangleup 0 = -1-(5)(0)$ $ \hphantom{-1 \bigtriangleup 0} = -1$ Now, find $-4 \oplus -1$ $ -4 \oplus -1 = (-4)^{2}+4(-1)^{2}$ $ \hphantom{-4 \oplus -1} = 20$.